It’s not an all or nothing with the economy and the president, but they do have some sway in some ways. Easy examples would be Biden’s Build Back Better Plan can help change the American economy, and if he does get elected to a second term, it will show results then.

On the other side, Trump pushed the Tax Cuts and Jobs Act. This has caused the deficit to climb, and didn’t help spur any economic growth (in fact:

A study by the Federal Reserve Bank similarly found that corporations bought-back stock and paid down debt, rather than undertake either new capital expenditure or investment in research & development.

And many of the issues of this truly Act became an issue starting in 2021, which if Trump was in office, would have been reflected on his presidency. (It’s part of the issues Biden has been having with the economy).

As most US presidents serve for 8 years (most win both terms), then such a lag would be noticed within their time in office. Your answer only applies to a small time frame, not an 8 year time frame

The Republicans in general have shown that for a while now. The last times the Republicans won the popular vote was in 2004 (Bush, only during his second term and considered to have only won that because of his leaning on 9/11) and Regan in 1988. If it wasn’t for the electoral college, most likely the last 30 years would have only been Democrats as President.

https://www.statista.com/statistics/1035521/popular-votes-republican-democratic-parties-since-1828/

And this would have most likely been a great thing for the USA as Democrats ower the deficit and Republicans raise it.

Not to mention that the economy is also typically better when a Democrat is the president.